1. Field of the Invention
The present invention is directed to a method and apparatus for rapid screening of volatiles in reaction products and, more specifically, to a method and apparatus for rapid screening of volatiles in complex combinatorial libraries.
2. Discussion of Related Art
Since its introduction in 1970, combinatorial chemistry has become a popular research tool among scientists in many fields. Combinatorial screening for biological activity has been prevalent in the pharmaceutical industry for nearly twenty years. Recently, combinatorial screening of catalysts for the chemical and materials industries has been developed and continues to be an attractive research method.
One of the many challenges in the development of combinatorial screening for production scale reactions is the difficulty involved in emulating production scale behavior at the micro-scale necessary for combinatorial work. Furthermore, rapid analytical techniques capable of measuring both the semi-quantitative and qualitative properties necessary for high throughput screening of combinatorial libraries continue to elude the industry. For example, high throughput screening of volatiles in complex combinatorial libraries presents unique problems for practitioners.
Traditional analysis methods for volatile species involve gas chromatography (GC), mass spectrometry (MS), GC/MS, and various spectroscopic techniques. The use of chemical sensors is an appealing alternative for detection of volatiles. In particular, chemical sensors potentially afford many attractive features for screening of combinatorial libraries such as ruggedness, small size, high sensitivity, and low cost. However, a single sensor often suffers from a non-specific response, making the identification and quantitation of species problematic. To address this issue, conventional chemical sensors have being utilized in combination with one another to form an array of sensors. The number of sensors in the array typically range from less than ten to thousands depending on the type of sensor response, complexity of analyzed mixture, concentration of each vapor component, signal and noise levels produced by each sensor, similarity of the vapor response patterns, and other factors.
Efforts to reduce the number of transducers in sensor arrays have been directed to measuring multiple parameters from a single sensing element. Although measurement of dual responses from a single sensing device ostensibly provides twice as much information as a single output sensor, this detection approach has traditionally exhibited several limitations, including the following:
1. Data analysis from a dual-response sensor is complicated because it may require multi-way calibration procedures.
2. Further complications can arise from nonlinear sensor response measured by one or both detection methods as a function of concentration of multiple analytes.
3. Information from a single sensor that operates in a dual-response mode is obtained at the cost of complication of the sensor design and reduction of its robustness.
4. Further increase of information content of such a sensor becomes problematic because it requires yet another measurement technique.
5. In a single sensor that operates in a dual-response mode, it is difficult to implement adequate signal referencing strategies for both detection methods.
As the demand for high performance materials continues to grow, new and improved methods of providing products more economically are needed to supply the market. In this context, various reactant and catalyst combinations are constantly being evaluated; however, methods for quickly and accurately determining the identities of chemically or economically superior reactant systems for industrial processes continue to challenge the industry. New and improved methods and devices are needed for rapid screening of potential reactant systems and catalysts.